The invention relates generally to mitigation of metal salt migration in carbon filters. In particular, the invention relates to using porphyrin impregnation to trap metal ions to inhibit their movement and chemical interaction within the filter.
Impregnated carbon is incorporated into filters designed for gas masks to protect respiratory systems from contamination. Activated Carbon, Impregnated with Copper, Silver, Zinc, Molybdenum, and Triethlyenediamine (ASZM-TEDA) constitutes a filtration material used in conjunction with standards MIL-DTL-32101A and EA-C-1704 (Army).
The compound material ASZM-TEDA constitutes an adsorbent conventionally used in the military's chemical and biological protection systems to capture and destroy chemical threats. ASZM-TEDA consists of an activated carbon with metal salts adsorbed into the pores to provide the reactivity towards chemical weapon agents. The carbon (C) adsorbs the threat agents and the metal salts neutralizes these threats by chemical reaction. After three or four years of service life, the carbon becomes less effective at stopping particular chemical threats, especially those with higher volatility. Such threats include blood agents including hydrogen cyanide (HCN) and cyanogen chloride (CNCl).
Hydrogen cyanide has NATO weapon designation “AC”, being an organic compound called prussic acid. AC is a colorless, extremely poisonous liquid that boils at slightly above room temperature at 25.6° C. (78.1° F.), and is produced on an industrial scale as a highly valuable precursor to many chemical compounds ranging from polymers to pharmaceuticals.
Cynogen chloride has NATO weapon designation “CK” and is a corrosive, colorless gas at low temperatures, readily condensable into a clear, colorless liquid with an irritating, pungent odor. CK dissolves slowly in water, reacting therewith to form hydrogen chloride (HCl) gas. CK has a molecular weight of 61.47, which translates to a vapor density of 2.12, thereby sinking in air to collect in low spots and confined areas. CK boils at 13.8° C. (56.84° F.), freezes at −6.0° C. (21.2° F.), and evaporates rapidly in contact with exposed water. CK has the additional hazard of being able to polymerize, usually explosively.